Mobile devices are becoming ubiquitous. People carry them to meetings, use them out of the office, in social situations, and in other settings where wireless communication is needed. Incoming voice calls to mobile devices can be intrusive under certain situations. It is therefore desirable to allow callees to screen calls and decide in advance whether the calls warrant answering. Caller ID service is conventionally available to provide a callee with limited information about a call for call screening purposes, with the callee usually having very few options to manage the call. In particular, for most callees, the only available actions are to accept the call or decline it by either not answering or allowing an answering machine or voice mail system to respond. The caller in such cases has no control over whether or not the call will be accepted.
More advanced Caller ID services can provide the callee with limited interaction with the caller to assist the call screening process, thereby giving both the caller and the callee more control over the call. However, despite the limited interaction, the caller still has no effective way of knowing when the callee is willing to accept their call.
There are models and mechanisms such as those defined by the presence and availability management (PAM) standards that allow a caller to discover the willingness of a callee to receive a call. PAM provides a set of APIs that a caller's mobile application software can use to check for the availability of a callee. However, the PAM only provides what a user of a mobile phone provides such as online, offline, in a meeting, etc. The PAM does not specifically provide the current status or operating mode of the mobile phone.